Tension device



w, .1935 H. Y. ARMSTRONG Q zflfiggw TENSION DEVICE 7 Filed April 5, 1934ATTORNEYS.

Patented Dec. 10, 1935 UNITED STATES PATENT OFFICE 7 Claims.

This invention relates to a device for maintaining a uniform tensionupon a rotatable shaft, or to yieldably resist the rotation of a shaft.

An object of the invention is a device which will '5 at all timesyieldably resist the rotation of a rotatable member with a uniformresistance.

Another object of the invention is a device which tends to effectretrograde rotation to the rotatable member, to prevent over-running of10 the rotatable member, particularly a rotatable member having anintermittent feeding movement.

Another object of the invention is a device of the class referred towhich is of maximum sim- 15 plicity, and of minimum cost to manufacture.

Another object of the invention is a device, of the class referred to,which can be readily and easily removed, or disconnected, from the shaftand replaced thereon without necessitating any 20 adjustments, or theservices of a skilled operator, and which is impossible to get out oforder.

The invention consists in the novel features and in the combinations andconstructions hereinafter set forth and claimed.

25 In describing this invention, reference is had to the accompanyingdrawing in which like characters designate corresponding parts in allthe views.

Figure 1 is a side elevation of the device se- 30 cured to a rotatableshaft which carries, and from which is unwound, a roll of web material.

Figure 2 is an end elevation of the structure shown in Figure 1.

Figure 3 is a partial plan view of the tension 35 device.

Figures 4, 5, 6 and '7 are end elevations of the tension device showingsuccessive stages of the operation of the device during rotation of theshaft.

40 The invention consists generally in a shaft, suitable bearings forrotatably supporting the shaft, a cylindrical body, or worm, providedwith a helical thread, or groove, on its periphery, a cord secured tothe body and arranged to thread into 45 said groove, and a weightsuspending from the free end of the cord, the shaft and the cylindricalbody constituting one form of rotatable member.

in designates a shaft which is rotatably mount- 50 ed in suitablebearings ll. As here shown, the bearings are secured to the frame work[2.

I3 designates a roll of paper, or sheet material, in the form of a web,which is temporarily secured to the shaft I in any suitable manner,

55 and rotatable therewith.

The frame I2 may consist of a part of any machine performing operationsupon the web I4 as it is unrolled from the roll l3, as for example,

a bread wrapping machine, or a stamping machine for fabricating articlesfrom the web [4. 5 Obviously, the web It may be metallic, or fibrous,and may be in the form of a band or wire. Usually, where a web isunrolled from a roll, as referred to, the web is moved, or indexed,along by suitable mechanism whereby the operations on the web may besuccessively carried on. Where the roll is permitted to freely rotateupon the shaft, or the shaft permitted to freely rotate in its bearings,an appreciable amount of slack in the web is effected during itsmovement through the machine. This results from the inertia, orcoastingeffect of the roll which often is considerable, particularly when theroll is of large diameter and results in an appreciable amount of slackin the web, which is undesirable and often affects the indexing, orproper progression, of the web through the machine.

Various forms of friction devices are commonly employed to maintain atension on the shaft, or the roll of material. However, the tension ofsaid devices varies greatly due to wear of the friction elements,atmospheric conditions, changes in temperature, and the like. Veryoften, the web is exceedingly thin, and dimculties are incurred as theresult of the changes in the resistance of the friction devices.

The frame 12, or its equivalent, is usually provided with automaticmeans to prevent retrograde movement of the web it after it has beenindexed, or moved, from one station to the next of the forming machine.As here shown, this means comprises a cam or eccentric 55 provided witha weighted portion or handle l6 which tends to rotate the eccentric I 5in a clockwise direction,

and clamp the web l4 between theeccentric and 40 the top of the frameI2. Any retrograde movement of the web It obviously tends to tighten theeccentric or the cam 55, tighter. Any suitable means, in place of theeccentric it, may be used to prevent retrograde movement of the web 14.

The tension device proper consists of a cylindrical body I! which isformed on its periphery, or provided, with a helical groove, 01 threadI8. The member I! is secured to the shaft It in any suitable manner, butpreferably so that it may .be readily removed from the shaft l0 andreplaced thereon. As here shown, the body I! is provided with a bore toslidably receive the end of the shaft Ill, and is secured thereto, androtatable therewith, by means of the key IS. The

body I1 is arranged on the end of the shaft so that the end of the shaftterminates in, or within, the plane of the end of the body, and thehelical thread, or groove I8 is so formed that it tends to threadoutwardly toward the end of the body,

upon rotation of the shaft ID in the desired direction to effectunrolling of the Web I4.

20 designates a cord, or similar flexible element, such as a chain,rope, cable, band, or the 10 like. One end of the cord 20 is secured tothe body I! as at 2|, andthe cord is:threaded into the groove I8. Aweight 22 is suspended from the free end of the cord.

Referring to Figure 2 of the drawing, it will be observed that theunwinding of the web I4 will effect rotation of the shaft II! inaclockwise .di-. rection. Accordingly, if the thread of the body II,which is secured to the rightend of the shaft Figure 1, is right handed,the cord will, upon 20 unwinding of the web I 4 from roll I3, threadonto the body I], .and the weight v22 .willmove upwardly .and outwardly.When the cord 20 reaches -.the .endof the thread or groove I8, thefreeportion of the cord 26 will drop off from the body II. This actionis illustrated in Figures 4 to 7 inclusive.

.In Figure .4, .the .cord has been wound in the groovexupon the body I1,and has approached the end 101' the groove, or thread indicated at 23.

39' Further rotation of the body II, in a clockwise direction, .Figure5, will bring the end of the threadat the top side of the body, asindicated in Figure 5. In this position, .due to the fact that thegroove or thread I8 now has only one side,

the cord 25 will feed off, or drop out, of the grooveover the end of thebody and the shaft.

Figure 6 represents rotation of the shaft and body through an arc of 45,over that shown in Figure 5. It will be observed that in this position,the cord 20 is dropping out of thergroove I8 and overthe end of thebody.

Figure 7 designates the same relative position of the shaft and body, asshown in Figure 6, but withthe .cord dropped-out of the threadforapproximately one-half the circumference of the body. It will beunderstood that when the end 23 .of the thread I8 reachesits uppermostposition, as in Figure 5, and the cord has noouter wall to retain it, itdrops 01f immediately. In

other words, the operation indicated in Figures 5, 6 and 7, isconsummated instantaneously.

It Will be observed, Figure 7, that the cord has again assumed aposition tangential to the rear side of the body, and is now eifectiveto establish 1 resistance to the rotation of the shaft in a clockwisedirection. Upon rotation of the shaft and the body, the operations shownin Figures 4 to 7 inclusive, again take place. In other words, the cord20 never becomes wound up upon the body 0 I1, and during the winding upof the cord the tension is uniform in that it is effected by the weight22.

It will be observed that the weight 22 tends to rotate the shaft II] andthe roll I3 in a retrograde, or counter-clockwise, direction, Figures 2to 7. Accordingly, in addition to establishing a tension, or yieldableresistance, to the rotation of the roll I3 in a clockwise direction, thedevice will, in the event of the formation of any slack 0 in the webbetween the roll I3 and the lock I5, immediately rotate the roll inreverse direction, and remove the slack. This feature of my device is.of .appreciable importance. In friction devices heretofore used, atension is maintained upon'the web I4. However, asa webis indexed, ormoved along, through the forming machine, a certain amount of slack inthe web is created during each indexing movement, and in as much as thefriction device holds the roll I3 from rotation in both directions, thisslack is gradually built up and eventually creates an undesirablesituation, permitting the web to become entangled in the operatingmachine, or pile up upon the floor. With my device, any slack created bythe unwinding of the web It is immediately taken up. 10 In'instanceswhere the additional resistance, caused by the cord dropping ofi overthe end of .the body, is objectionable, the cord 20 may be provided witha helical tension spring 25, or the equivalent, to lessen, or dampen,the shock caused 15 by the weight falling a distance equal tosubstantially'the diameter of the body II. It will be observed that asthe cord passes out of the groove I8 and drops over the end of the body,a rotary motion will be imparted to the weight which may, 29 insomeinstances, increase the wear on the cord 20. ..To avoidthissituation, the cord 20 may also be providedwith a swivel device 26 whichalso assists in preventing a swinging movement to the weight. 25 Inorder to maintain a retrograde force on the shaft and preventover-running when the coil is being displaced, and hence, theshaftmomentarily released of the braking force of the weight whenthe cord.and weight are passing from the 30 position shown in Figure 6 to thatshown inFigure '7, the shaft Ill may be provided with a similardevice atits opposite end, as shown in Figure 1. In this instance, the body I Iof one device would be secured to the shaft Ill insuch'manner that theend 23 of the groove or thread I8 would assume a relationship wherebythe end of the groove I8 on the other body would be offsetsubstantiallyWith this structure, one-of the cords 20 would always be winding up whenthe 40,

other cord dropped over the end of the other body.

The resistance required under different conditions and for differentwebs can be readily varied by adding to, or subtracting from, the 45weights 22. This may be accomplished by forming the main portion of theweight 22 with a stem 28 connecting the ends of the weight, andadditional weights may be inserted between :the

ends, the additional weightsbeing provided with 50,

a slot to'receive the stem 28.

It will be observed that by my device, ,Imot only maintain substantiallyuniformtension upon theroll I3, but I also maintain a uniformretrogradeforce. Also, on account of its extremesim- 55,

plicity,. there is nothing in my device to become out of order, and thedevice may bereadily removed and replaced on the ends of the shaft Ill.The operation of the device is fully automatic, as rotation of the rollI3 and shaft I0 eventually 0 wind up the cord 20, and as the bodies Iare secured to theshaft in a predetermined position by the key I9,'thedevice may be removed and replaced on the .shaft'b-y any unskilledlabor.

'What I claim is:

1. .The combination of a rotatable shaft,.a cylindricalbody secured toone'end' thereof "and rotatable therewith, said body being formed on itsperiphery with -a helical groove, a cord having one endsecured to thebody and arranged to :be 7.0.

wound on the body in the groove upon rotation of the shaftinone-direction and to threadout of the groove and off of the body overthe end thereof, a'xweight suspended from the free end of the cord, andmeans to prevent rotation of 75 the weight about its vertical axis whenthe cord threads off the end of the body.

2. The combination of a rotatable shaft, a cylindrical body secured toeach end of the shaft with the ends of the shaft terminating within theplanes of the outer sides of the bodies, the bodies being provided witha helical groove threading outwardly toward the outside of the bodiesupon rotation of the shaft in one direction, a cord secured to each ofsaid bodies and being arranged to wind upon the bodies upon rotation ofthe shaft, and a weight suspended from the free end of each cord.

3. The combination of a rotatable member, a cord winding on the memberand having means for applying tension in opposition to the rotation ofthe member, the member having means for periodically displacing off theend of said member the last coil of the cord contiguous of the portionconnected to the tensioning means and initially tangent to said member,whereby the tensioning means is free to react and return said portion ofthe cord to its original tangential relation to the rotating member andapply a momentary braking impulse to the member.

4. The combination of a rotatable member, a cord winding on the memberand having means for applying tension in opposition to the rotation ofthe member, the member having means for periodically displacing off theend of said member the last coil of the cord contiguous of the portionconnected to the tensioning means and initially tangential to saidmember, whereby the tensioning means is free to react and return saidportion of the cord to its original tangential relation to the rotatingmember and apply a momentary braking impulse to the member, saiddisplacing means comprising a helical groove in the rotating member-inwhich the last coil lies, the groove breaking through the end face ofthe rotating member at a location where the cord is initially tangent tothe member, whereby the portion of the cord continuous of the last coilshifts crosswise of the end face of the rotatable member as said memberrotates and said location shifts about the axis of said member.

5. The combination of a rotatable member, a cord winding on the memberand having means for applying tension in opposition to the rotation ofthe member, the member having means for periodically displacing off theend of said mem- 5 ber the last coil of the cord contiguous of theportion connected to the tensioning means and extending tangential tosaid member, whereby the tensioning means is free to react and returnsaid portion of the cord to its original tangential relation to therotating member and apply a momentary braking impulse to the member, andmeans tending to rotate said 'member in a retrograde direction when thecord is returning to its original tangential relation to the rotatablemember.

6. The combination of a rotatable member, cords winding on the member,and each having means for applying tension in opposition to the rotationof the member, the rotatable member having helical grooves in each ofwhich the last coil of each cord lies, each groove breaking through anend face of the rotating member at a location where the cord therein isinitially tangent to the member, whereby the portion of the cordcontiguous of the last coil shifts crosswise of the end face of therotatable member as said member rotates and said location shifts aboutthe axis of the rotatable member, the location where the grooves openthrough the end face of the rotatable members being so arranged thateither of said cords is in position to apply retrograde movement to therotatable member, when the other is displaced from the rotatable member.

'7. The combination of a rotatable member, of means for continuously andyieldingly resisting rotation of said member including a cord winding onthe member and traveling toward the end of the member and having meansfor applying 40 tension in opposition to the rotation of the member, themember having means for periodically displacing off the end of themember the last coil of the cord and subsequently, rewinding thedisplaced portion of the cord.

HARRY Y. ARMSTRONG.

